Scanning tunneling microscopy of Bi$_2$Te$_3$ films prepared by pulsed laser deposition: from nanocrystalline structures to van der Waals epitaxy

TL;DR

This study explores the growth of Bi$_2$Te$_3$ films via pulsed laser deposition, revealing that van der Waals epitaxy is achievable with a background gas, supported by microscopy, spectroscopy, and theoretical calculations.

Contribution

It demonstrates the conditions under which van der Waals epitaxy of Bi$_2$Te$_3$ can be achieved using pulsed laser deposition with background gas, combining experimental and theoretical insights.

Findings

Van der Waals epitaxy of Bi$_2$Te$_3$ is possible with background gas.

Scanning tunneling microscopy reveals nanocrystalline to epitaxial structures.

Ab initio calculations match tunneling spectra of epitaxial films.

Abstract

Bi$_2$Te$_3$ is a material with high efficiency of thermoelectric energy conversion. Recently, it was also recognized as a topological insulator, and is often used as the basis for creation of other types of topological matter. Pulsed laser deposition (PLD) is widely considered as a simple method for growing of multicomponent films, but not as a tool for van der Waals epitaxy. We demonstrate here that the van der Waals epitaxy of Bi$_2$Te$_3$ is indeed impossible in vacuum PLD, but is possible in the presence of a background gas, which is confirmed by the results of scanning tunneling microscopy and spectroscopy studies. Results of {\it ab initio} calculations reproduce tunneling spectra of the first three terraces of epitaxial films of Bi$_2$Te$_3$. In addition, an unusual hexagonal superstructure resembling a charge-density wave is observed in overheated films.